174 IMMUNE SERA 



incubation. Here the second injection comes at a 

 time when the accumulation of antibodies is at its 

 height. It has been claimed that this explains the 

 cases of sudden death in humans following injec- 

 tions of serum, but investigation shows that most 

 of these deaths occurred after but a single injection 

 of serum. Moreover in most of them such conditions 

 as status lymphaticus sufficed to explain the fatal 

 ending. 



This theory has found some experimental con- 

 firmation from the work of Vaughan and Wheeler, 

 who have been able to prepare a number of split 

 products from the proteid molecule, some of which 

 in animals give rise to a symptom complex not 

 unlike that of t}^pical anaphylaxis. 



Allergy. It is apparent that what has been said 

 concerning the production of anaphylaxis in re- 

 sponse to serum injections will apply also to bac- 

 terial infections, for in these the body is injected, 

 as it were, with bacterial proteids. The phenomena 

 of anaphylaxis are therefore of general application in 

 immunity. This is well expressed by von Pirquet, 1 

 who calls attention to the fact that the main differ- 

 ence between a normal and an immune individual 

 is one relating to the alteration in the latter's re- 

 activity. He speaks of this alteration as "allergy": 

 from ergeia, reactivity, and olios, altered, meaning 

 thereby a changed reactivity as a clinical conception 



1 C. E. von Pirquet, Archives of Internal Medicine, Feb. 1911. 



